Potential sensitive dyes

Waggoner AS, Grinvald A (1977) Mechanisms of rapid optical changes of potential sensitive dyes. Ann N Y Acad Sci 303 217-241... 

Wolfbeis O.S., Fluorescence-based ion sensing using potential-sensitive dyes, Sensor ActuatB-Chem 1995 29 140. 

Murkovic I., Lobnik A., Mohr G.J., Wolfbeis O.S., Fluorescent potential-sensitive dyes for use in solid-state sensors for potassium ion, Anal. Chim. Acta, 1996 334 125. 

The fourth type of mediator-based cation optical sensing is using potential sensitive dye and a cation selective ionophore doped in polymer membrane. Strong fluorophores, e.g. Rhodamine-B C-18 ester exhibits differences in fluorescence intensity because of the concentration redistribution in membranes. PVC membranes doped with a potassium ionophore, can selectively extract potassium into the membrane, and therefore produce a potential at the membrane/solu-tion interface. This potential will cause the fluorescent dye to redistribute within the membrane and therefore changes its fluorescence intensity. Here, the ionophore and the fluorescence have no interaction, therefore it can be applied to develop other cation sensors with a selective neutral ionophore. 

Baxter DF, Kirk M, Garcia AF et al. (2002) A novel membrane potential-sensitive fluorescent dye improves cell-based assays for ion channels. J Biomol Screen 7(1) 79—85 Epps DE, Wolfe ML, Groppi V (1994) Characterization of the steady-state and dynamic fluorescence properties of the potential-sensitive dye bis-(l,3-dibutylbarbituric acid)trimethine oxonol (BiBAC4(3)) in model systems and cells. Chem Phys Lipids 69(2) 137—150 Gonzalez JE, Maher MP (2002) Cellular fluorescent indicators and voltage/ion probe reader (VIPR(TM)) tools for ion channel and receptor drug discovery. Recept Channels 8(5—6) 283—295... 

The interface between two immiscible liquids is used as a characteristic boundary for study of charge equilibrium, adsorption, and transport. Interfacial potential differences across the liquid-liquid boundary are explained theoretically and documented in experimental studies with fluorescent, potential-sensitive dyes. The results show that the presence of an inert salt or a physiological electrolyte is essential for the function of the dyes. Impedance measurements are used for studies of bovine serum albumin (BSA) adsorption on the interface. Methods for determination of liquid-liquid capacitance influenced by the presence of BSA are shown. The potential of zero charge of the interface was obtained for 0-200 ppm of BSA. The impedance behavior is also discussed as a function of pH. A recent new approach, using a microinterface for interfacial ion transport, is outlined. 

Figure 1. Time dependence of fluorescence quenching of the potential-sensitive dye DisC2 in the presence of 0.1-mg/mL CD vesicles in 2 X 10 5-M NaCl upon addition of 0.1-M PEI+ and different amounts of alamethicin to the outer phase. The excitation wavelength was 620 nm and emission wavelength was 670 nm. (Reproduced with permission from reference 8. Copyright 1990 Elsevier.)...

That these sensors have practical significance is illustrated by the publications of Hisamoto et al. and Wang et al, which have described the measurement of common ions directly in serum [228, 229]. Alternatively, the complexation of the metal ion may influence the partition of the lipophilic dye in the membrane phase, which can affect the fluorescence yield of the dye. Recently this principle has been demonstrated with potential sensitive dyes by Wolfbeis and Mohr [231, 232]. This approach is also applicable to the sensing of neutral species and anions, as exemplified by sensor matrices for 2-phenetylamine [233] and nitrate [234]. 

Assays with externally added probes include the potential-sensitive dye safranin O (Figure 8). This cationic dye only loosely associates with an unpolarized vesicle membrane but binds more efficiently when an inside negative membrane potential is applied. This translocation into a more hydrophobic environment is accompanied with an increase in fluorescence and thereby reports on the extent of the applied membrane potential (Section A.A) ... 

Doranz, B. J. Lipid particles containing ion channels and membrane potential-sensitive dyes and their use in screening for effectors of ion channels. PCX Int. Appl. WO 2007089582, 2007 Chem. Abstr. 2007, 147, 250560. 

Ganapathy, V Burckhardt, G. Leibach, F. H. Peptide transport in rabbit intestinal brush-border membrane vesicles studied with a potential-sensitive dye. Biochim. Biophys. Acta 1985,816, 234-240. 

In this paper we describe the ATP-dependent membrane energization by the use of the surface charge density probe TDACMA, the electric potential-sensitive dye oxonol VI and natural carotenoids and the pH indicators neutral red and cresol red, trapped inside the vesicles, and their sensitivity to the iono-phores valinomycin and nigericin. 

Ortho esters, in synthesis of symmetrical trimethine thiazolocyanines, 54 Oxazolone, for neutrocyanines, 27 Oxidation potentials, of dyes, 75 of mesosubstituted dyes, in relation with absorption, 77 of polymethine dyes, 72 Oxidoreduction, relation between sensitizers, and silver halides, 78 4-Oxo-disubstituted 2-aminoselenazoles, table of products, 262 Oxonols, nomenclature of, 26 in synthesis of dimethine neutrocyanines, 62... 

Electric field sensitive dyes respond to changes in electrical membrane potential by a variety of different mechanisms with widely varying response times depending on their chemical structure and their interaction with the membrane. An understanding of the mechanisms of dye response and their response mechanisms is important for an appropriate choice of a probe for a particular application. The purpose of this chapter is, therefore, to provide an overview of the dyes presently available, how they respond to voltage changes, and give some examples of how they have been applied. Finally, because there is still scope for the development of new dyes with improved properties, some directions for future research will be discussed. 

Up to now in this chapter, we have concentrated on the measurement via electric field sensitive dyes of the transmembrane electrical potential, which by itself should produce a linear drop in the electrical potential across a membrane. However, at least through the lipid matrix of a cell membrane, the electrical potential, /, at any point does not change linearly across the membrane. Instead, it follows a complex profile (see Fig. 6). This is due to contributions other than the transmembrane electrical potential to /. The other contributions come from the surface potential and the dipole potential. Both of these can also be quantified via electric field sensitive dyes. 

The ideal electric field sensitive dye would respond to changes in intramembrane field strength or transmembrane electrical potential within femtoseconds the magnitude of its absorbance or fluorescence response would be enormous it would... 

Zochowski M, Wachowiak M, Falk CX et al (2000) Imaging membrane potential with voltage-sensitive dyes. Biol Bull 198 1-21... 

Schummer, U., Schiefer, H. G. and Gerhardt, U. (1979). Mycoplasma membrane-potentials determined by potential-sensitive fluorescent dyes. Curr. Microbiol. 2, 191-194. 

Petersons pH probe also was modified in order to give a miniature fiber optic sensor potentially suitable for glucose measurements90. Kopelman et al.91 developed a fiber-optic pH nanosensor for physiological measurements using a dual-emission sensitive dye. The performance of a pH sensor was reported92. An unclad fiber was dip-coated with a thin layer of porous cladding within which a pH-sensitive dye was entrapped. The fundamental... 

A novel approach for ion sensing is based on the use of potential-sensitive or polarity-sensitive dyes (PSDs) and was presented first106 in 1987. PSDs are charge dyes and typically located at the interface between a lipophilic sensor phase and a hydrophilic sample phase. The transport of an ion into the lipophilic sensor layer causes the PSD to be displaced from the hydrophilic/hydrophobic interface into the interior of the respective phase (or vice versa), thereby undergoing a significant change in its fluorescence properties107 110. 

The ion sensing scheme based on the use of potential-sensitive or polarity-sensitive dyes (PSDs) was extended to other anions. Both the clinically significant chloride ion124 and the environmentally important nitrate anion125 can be sensed in the desired concentration ranges. Such sensors have the unique advantage of having a virtually pH-insensitive response. 

Potential-sensitive or polarity-sensitive dyes are known to optically respond to changes in their micro-environment such as changes in polarity or lipophilicity. 

---